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Abstract

The antigenicity of lipids is still ill-defined, and there is very little evidence that any pure lipid by itself will act as an antigen . To produce an immune response they must be complexed with or coupled to carriers (1-6) . Only glycosphingolipids and phosphatides have been found to function as haptens when mixed with carriers such as serum albumin (7), methylated bovine serum albumin (8), or other auxillary lipids (9-11), or when the glycolipid was incorporated into liposomes (12). Antibodies to glycolipids are usually directed primarily against the carbohydrate moiety (1, 7, 13, 14), and there is little evidence that antibodies can be formed to the free lipids even though free fatty acids were reported to cause inflammatory delayed-type allergic skin reactions (15, 16).

The purpose of this investigation was to synthesize and study the antigenicity and immunological properties of a series of glycolipid antigens prepared by coupling isomaltose oligosaccharides - varying in size from isomaltose to isomaltoheptaose - to a lipid carrier, stearylamine, and to compare the antigenicities of the different stearylisomaltosyl oligosaccharides thus obtained, either when injected alone or when incorporated into liposomes. Isomaltose oligosaccharides were chosen because they are the predominant structural units of α1→6 dextran (17). Antibodies raised to them should cross-react with dextrans, and the heterogeneity of the response and the sizes of their antibody combining sites could be studied by quantitative precipitin and precipitin inhibition assays and could be compared with antidextran (18-22) .